Supported olefin polymerization catalyst

ABSTRACT

Supported catalyst systems are provided comprising (a) a transition metal compound, (b) an activator comprising (iii) an aluminoxane or (iv) a Group IIIA metal or metalloid compound, and (c) a support material comprising an inorganic metal oxide, inorganic metal halide or polymeric material or mixtures thereof characterised in that the support material has been pretreated with a source of a transition metal atom. The preferred transition metal compounds are metallocenes and the source of the transition metal atom is typically a ferrous or cupric metal salt. The supported catalyst systems show improved activity and also may reduce fouling in gas phase fluidised bed processes.

The present invention relates to supported catalysts and in particularto supported catalysts for use in the gas phase (co-) polymerisation ofolefins in a fluidised bed reactor.

Processes for the co-polymerisation of olefins in the gas phase are wellknown in the art. Such processes can be conducted for example byintroducing the gaseous monomer and comonomer into a stirred and/or gasfluidised bed comprising polyolefin and a catalyst for thepolymerisation.

In the gas fluidised bed polymerisation of olefins, the polymerisationis conducted in a fluidised bed reactor wherein a bed of polymerparticles is maintained in a fluidised state by means of an ascendinggas stream comprising the gaseous reaction monomer. The start-up of sucha polymerisation generally employs a bed of polymer particles similar tothe polymer which it is desired to manufacture. During the course ofpolymerisation, fresh polymer is generated by the catalyticpolymerisation of the monomer, and polymer product is withdrawn tomaintain the bed at more or less constant volume. An industriallyfavoured process employs a fluidisation grid to distribute thefluidising gas to the bed, and to act as a support for the bed when thesupply of gas is cut off. The polymer produced is generally withdrawnfrom the reactor via a discharge conduit arranged in the lower portionof the reactor, near the fluidisation grid. The fluidised bed consistsin a bed of growing polymer particles. This bed is maintained in afluidised condition by the continuous upward flow from the base of thereactor of a fluidising gas.

The polymerisation of olefins is an exothermic reaction and it istherefore necessary to provide means to cool the bed to remove the heatof polymerisation. In the absence of such cooling the bed would increasein temperature and, for example, the catalyst becomes inactive or thebed commences to fuse. In the fluidised bed polymerisation of olefins,the preferred method for removing the heat of polymerisation is bysupplying to the polymerisation reactor a gas, the fluidising gas, whichis at a temperature lower than the desired polymerisation temperature,passing the gas through the fluidised bed to conduct away the heat ofpolymerisation, removing the gas from the reactor and cooling it bypassage through an external heat exchanger, and recycling it to the bed.The temperature of the recycle gas can be adjusted in the heat exchangerto maintain the fluidised bed at the desired polymerisation temperature.In this method of polymerising alpha olefins, the recycle gas generallycomprises the monomer and comonomer olefins, optionally together with,for example, an inert diluent gas such as nitrogen or a gaseous chaintransfer agent such as hydrogen. Thus, the recycle gas serves to supplythe monomer to the bed, to fluidised the bed, and to maintain the bed atthe desired temperature. Monomers consumed by the polymerisationreaction are normally replaced by adding make up gas or liquid to thepolymerisation zone or reaction loop.

It is also well known that fouling in gas phase polymerisation processcan be a major problem, and can be caused by non-uniform fluidisation aswell as poor heat transfer in the polymerisation process. Catalyst andpolymer particles may adhere together or to the walls of the reactor andcontinue to polymerised, and often fuse together and form chunks, whichcan be detrimental to a continuous process, particularly a fluidised bedprocess

The incorporation of antistatic agents in polymerisation catalysts iswell known. For example U.S. Pat. No. 5,414,064 describes the use ofStadis with chromium based catalysts while U.S. Pat. No. 5,498,581describes again the use of Stadis with silica supported metallocenecatalyst systems.

U.S. Pat. No. 6,469,111 describes the gas phase polymerisation ofolefins using a catalyst system containing an antistatic agent based onmagnesium oxide or zinc oxide. The oxides are used in a mixture with asupported polymerisation catalyst component. The catalyst systemsdescribed therein include supported chromium oxide catalysts and alsosupported metallocene complexes in particular bis(cyclopentadienyl)metallocene complexes.

More recently WO 02/066524 describes supported catalysts for olefinpolymerisation comprising a combination of a sulfated metal oxidesupport and an aluminoxane. The sulphated metal oxide support may beeasily prepared by contacting a precursor metal oxide with a materialhaving a SO₄ group such as sulphuric acid or ammonium sulphate.Typically the resultant aluminoxane deposited on the sulphated metaloxide is used with an organometallic complex of a Group 4 metal, inparticular with metallocene complexes comprising both a cyclopentadienylligand and a phosphinimine ligand.

U.S. Pat. No. 6,107,230 describes catalyst compositions comprisinginorganic metal oxides impregnated with metal salts eg. cupric sulfate,metallocenes and organoaluminium compounds. The compositions may becombined together or preferably added separately into the reactor. Animportant aspect of this disclosure is that traditional activators suchas aluminoxanes, borates or magnesium chloride are not required.

We have now found that the incorporation of a transition metal atom intothe support material of a supported polymerisation catalyst system mayhave beneficial effects for activity as well as resulting in decreasedstatic levels on the resultant polymers.

Thus according to the present invention there is provided a supportedcatalyst system suitable for the polymerisation of olefins comprising

-   -   (a) a transition metal compound,    -   (b) an activator comprising        -   (i) an aluminoxane or        -   (ii) a Group IIIA (CAS Version) metal or metalloid compound,            and    -   (c) a support material comprising an inorganic metal oxide,        inorganic metal halide or polymeric material or mixtures thereof        characterised in that the support material has been pretreated        with a source of a transition metal atom.

The source of the transition metal atom is preferably an organic or aninorganic metal compound and is preferably a metal salt.

The preferred transition metal salts are for example metal salts ofiron, copper, cobalt, nickel and zinc. The preferred metal salts arethose of iron and copper.

The preferred salts are sulphates, nitrates, phosphates or acetates. Themost preferred salts are sulphates.

Also suitable are acid salts such as gluconates for example ferrousD-gluconate dihydrate.

Particularly preferred salts for use in the present invention areferrous sulphate (FeSO₄) and cupric sulphate (CuSO₄).

The most preferred support material for use with the catalyst systemaccording the present invention are inorganic metal oxides in particularoxides of aluminium, silicon, zirconium, zinc and titanium. Alumina,silica and silica-alumina are preferred metal oxides. Suitable silicasinclude Crosfield ES70, Davison 948 and Sylopol 948 silicas.

The support material is preferably treated with a water solution of therequired transition metal salt.

The support material may then be further subjected to a heat treatmentand/or chemical treatment to reduce the water content or the hydroxylcontent of the support material. Typically chemical dehydration agentsare reactive metal hydrides, aluminium alkyls and halides. Prior to itsuse the support material may be subjected to treatment at 100° C. to1000° C. and preferably at 200 to 850° C. in an inert atmosphere underreduced pressure.

The support material may be further combined with an organometalliccompound preferably an organoaluminium compound and most preferably atrialkylaluminium compound in a dilute solvent.

The support material is pretreated with the organometallic compound at atemperature of −20° C. to 150° C. and preferably at 20° C. to 100° C.

Other suitable support materials include Group IIa metal halides forexample magnesium chloride or polymeric materials such as finely dividedpolyolefins for example finely divided polyethylene.

The transition metal content on the support material is typically in therange 0.001% to 10%.

Suitable transition metal compounds for use in the catalyst system ofthe present invention are those based on the late transition metals(LTM) of Group VIII for example compounds containing iron, nickel,manganese, ruthenium, cobalt or palladium metals.

Examples of such compounds are described in WO 98/27124 and WO 99/12981and may be illustrated by[2,6-diacetylpyridinebis(2,6-diisopropylanil)FeCl₂],2.6-diacetylpyridinebis (2,4,6-trimethylanil) FeCl₂ and[2,6-diacetylpyridinebis(2,6-diisopropylanil)CoCl₂].

Other transition metal compounds include derivatives of Group IIIA, IVAor Lanthanide metals which are in the +2, +3 or +4 formal oxidationstate. Preferred compounds include metal complexes containing from 1 to3 anionic or neutral ligand groups which may be cyclic or non-cyclicdelocalized π-bonded anionic ligand groups. Examples of such π-bondedanionic ligand groups are conjugated or non-conjugated, cyclic ornon-cyclic dienyl groups, allyl groups, boratabenzene groups, phospholeand arene groups. By the term π-bonded is meant that the ligand group isbonded to the metal by a sharing of electrons from a partiallydelocalised π-bond.

Each atom in the delocalized α-bonded group may independently besubstituted with a radical selected from the group consisting ofhydrogen, halogen, hydrocarbyl, halohydrocarbyl, hydrocarbyl,substituted metalloid radicals wherein the metalloid is selected fromGroup IVB of the Periodic Table. Included in the term “hydrocarbyl” areC1-C20 straight, branched and cyclic alkyl radicals, C6-C20 aromaticradicals, etc. In addition two or more such radicals may together form afused ring system or they may form a metallocycle with the metal.

Examples of suitable anionic, delocalised π-bonded groups includecyclopentadienyl, indenyl, fluorenyl, tetrahydroindenyl,tetrahydrofluorenyl, octahydrofluorenyl, etc. as well as phospholes andboratabenzene groups.

Phospholes are anionic ligands that are phosphorus containing analoguesto the cyclopentadienyl groups. They are known in the art and describedin WO 98/50392.

The boratabenzenes are anionic ligands that are boron containinganalogues to benzene. They are known in the art and are described inOrganometallics, 14, 1, 471-480 (1995).

The preferred transition metal compound is a bulky ligand compound alsoreferred to as a metallocene complex containing at least one of theaforementioned delocalized π-bonded group, in particularcyclopentadienyl ligands. Such metallocene complexes are those based onGroup IVB (CAS Version) metals for example titanium, zirconium andhafnium.

Metallocene complexes may be represented by the general formula:LxMQnwhere L is a cyclopentadienyl ligand, M is a Group IVB metal, Q is aleaving group and x and n are dependent upon the oxidation state of themetal.

Typically the Group IVA metal is titanium, zirconium or hafnium, x iseither 1 or 2 and typical leaving groups include halogen or hydrocarbyl.The cyclopentadienyl ligands may be substituted for example by alkyl oralkenyl groups or may comprise a fused ring system such as indenyl orfluorenyl.

Examples of suitable metallocene complexes are disclosed in EP 129368and EP 206794. Such complexes may be unbridged eg. bis(cyclopentadienyl)zirconium dichloride, bis(pentamethyl)cyclopentadienyl dichloride, ormay be bridged eg. ethylene bis(indenyl) zirconium dichloride ordimethylsilyl(indenyl) zirconium dichloride.

Other suitable bis(cyclopentadienyl) metallocene complexes are thosebis(cyclopentadienyl) diene complexes described in WO 96/04290. Examplesof such complexes are bis(cyclopentadienyl) zirconium(2.3-dimethyl-1,3-butadiene) and ethylene bis(indenyl) zirconium1,4-diphenyl butadiene.

Examples of monocyclopentadienyl or substituted monocyclopentadienylcomplexes suitable for use in the present invention are described in EP416815, EP 418044, EP 420436 and EP 551277. Suitable complexes may berepresented by the general formula:CpMX_(n)

wherein Cp is a single cyclopentadienyl or substituted cyclopentadienylgroup optionally covalently bonded to M through a substituent, M is aGroup VIB (CAS Version) metal bound in a η⁵ bonding mode to thecyclopentadienyl or substituted cyclopentadienyl group, X eachoccurrence is hydride or a moiety selected from the group consisting ofhalo, alkyl, aryl, aryloxy, alkoxy, alkoxyalkyl, amidoalkyl, siloxyalkyletc. having up to 20 non-hydrogen atoms and neutral Lewis base ligandshaving up to 20 non-hydrogen atoms or optionally one X together with Cpforms a metallocycle with M and n is dependent upon the valency of themetal.

Particularly preferred monocyclopentadienyl complexes have the formula:

wherein:—

R′ each occurrence is independently selected from hydrogen, hydrocarbyl,silyl, germyl, halo, cyano, and combinations thereof, said R′ having upto 20 nonhydrogen atoms, and optionally, two R′ groups (where R′ is nothydrogen, halo or cyano) together form a divalent derivative thereofconnected to adjacent positions of the cyclopentadienyl ring to form afused ring structure;

X is hydride or a moiety selected from the group consisting of halo,alkyl, aryl, aryloxy, alkoxy, alkoxyalkyl, amidoalkyl, siloxyalkyl etc.having up to 20 non-hydrogen atoms and neutral Lewis base ligands havingup to 20 non-hydrogen atoms,

Y is —O—, —S—, —NR*—, —PR*—,

M is hafnium, titanium or zirconium,

Z* is SiR*₂, CR*₂, SiR*₂SIR*₂, CR*₂CR*₂, CR*═CR*, CR*₂SIR*₂, or

GeR*₂, wherein:

R* each occurrence is independently hydrogen, or a member selected fromhydrocarbyl, silyl, halogenated alkyl, halogenated aryl, andcombinations thereof, said

R* having up to 10 non-hydrogen atoms, and optionally, two R* groupsfrom Z* (when R* is not hydrogen), or an R* group from Z* and an R*group from Y form a ring system.,

and n is 1 or 2 depending on the valence of M.

Examples of suitable monocyclopentadienyl complexes are(tert-butylamido) dimethyl (tetramethyl-η⁵-cyclopentadienyl)silanetitanium dichloride and (2-methoxyphenylamido) dimethyl(tetramethyl-η⁵-cyclopentadienyl) silanetitanium dichloride.

Other suitable monocyclopentadienyl complexes are those comprisingphosphinimine ligands described in WO 99/40125, WO 00/05237, WO 00/05238and WO00/32653. A typical examples of such a complex is cyclopentadienyltitanium [tri (tertiary butyl) phosphinimine]dichloride.

Another type of transition metal compound suitable for use in thepresent invention are monocyclopentadienyl complexes comprisingheteroallyl moieties such as zirconium (cyclopentadienyl) tris(diethylcarbamates) as described in U.S. Pat. No. 5,527,752 and WO99/61486.

Particularly preferred metallocene complexes for use in the catalystsystem of the present invention may be represented by the generalformula:

wherein:—

R′ each occurrence is independently selected from hydrogen, hydrocarbyl,silyl, germyl, halo, cyano, and combinations thereof, said R′ having upto 20 nonhydrogen atoms, and optionally, two R′ groups (where R′ is nothydrogen, halo or cyano) together form a divalent derivative thereofconnected to adjacent positions of the cyclopentadienyl ring to form afused ring structure;

X is a neutral η⁴ bonded diene group having up to 30 non-hydrogen atoms,which forms a η-complex with M;

Y is —O—, —S—, —NR*—, —PR*—,

M is titanium or zirconium in the +2 formal oxidation state;

Z* is SiR*₂, CR*₂, SiR*₂SIR*₂, CR*₂CR*₂, CR*═CR*, CR*₂SIR*₂, or GeR*₂,wherein:

R* each occurrence is independently hydrogen, or a member selected fromhydrocarbyl, silyl, halogenated alkyl, halogenated aryl, andcombinations thereof, said

R* having up to 10 non-hydrogen atoms, and optionally, two R* groupsfrom Z* (when R* is not hydrogen), or an R* group from Z* and an R*group from Y form a ring system.

Examples of suitable X groups includes-trans-η⁴-1,4-diphenyl-1,3-butadiene,s-trans-η⁴-3-methyl-1,3-pentadiene; s-trans-η⁴-2,4-hexadiene;s-trans-η⁴-1,3-pentadiene; s-trans-η⁴-1,4-ditolyl-1,3-butadiene;s-trans-η⁴-1,4-bis(trimethylsilyl)-1,3-butadiene;s-cis-η⁴-3-methyl-1,3-pentadiene; s-cis-η⁴-1,4-dibenzyl-1,3-butadiene;s-cis-η⁴-1,3-pentadiene; s-cis-η⁴-1,4-bis(trimethylsilyl)-1,3-butadiene,said s-cis diene group forming a π-complex as defined herein with themetal.

Most preferably R′ is hydrogen, methyl, ethyl, propyl, butyl, pentyl,hexyl, benzyl, or phenyl or 2 R′ groups (except hydrogen) are linkedtogether, the entire C₅R′₄ group thereby being, for example, an indenyl,tetrahydroindenyl, fluorenyl, terahydrofluorenyl, or octahydrofluorenylgroup.

Highly preferred Y groups are nitrogen or phosphorus containing groupscontaining a group corresponding to the formula —N(R″)— or —P(R″)—wherein R″ is C₁₋₁₀ hydrocarbyl.

Most preferred complexes are amidosilane- or amidoalkanediyl complexes.

Most preferred complexes are those wherein M is titanium.

Specific complexes suitable for use in the catalyst system of thepresent invention are those disclosed in WO 95/00526 and areincorporated herein by reference.

A particularly preferred complex for use in the present invention is(t-butylamido) (tetramethyl-η⁵-cyclopentadienyl) dimethylsilanetitanium-η⁴-1.3-pentadiene.

Suitable activators for use in the present invention are aluminoxanes orGroup IIIA metal or metalloid compounds.

Aluminoxanes are well known as activators for metallocene complexes.Suitable aluminoxanes, for use in the catalyst system of the presentinvention, include polymeric or oligomeric aluminoxanes in particularmethyl aluminoxane (MAO).

Preferred Group IIIA metal or metalloid compounds are those wherein themetal is boron.

Particularly preferred Group IIIA metal or metalloid compounds arefluorine containing Group IIIA metal or metalloid compounds.

Suitable boron compounds are triarylboron compounds, in particularperfluorinated triarylboron compounds.

A particularly preferred triarylboron compound istris(pentafluorophenyl) borane (FAB).

Preferred Group IIIA metal or metalloid compounds suitable as activatorsfor use in the present invention are ionic compounds comprising a cationand an anion.

The cation is typically a Bronsted acid capable of donating a proton andthe anion is typically a compatible non-coordinating bulky speciescapable of stabilizing the cation.

Such activators may be represented by the formula:(L*−H)⁺ _(d)(A^(d−))

wherein

L* is a neutral Lewis base

(L*−H)⁺ _(d) is a Bronsted acid

A^(d−) is a non-coordinating compatible anion of a Group IIIA metal ormetalloid

having a charge of d⁻, and

d is an integer from 1 to 3.

The cation of the ionic compound may be selected from the groupconsisting of acidic cations, carbonium cations, silylium cations,oxonium cations, organometallic cations and cationic oxidizing agents.

Suitably preferred cations include trihydrocarbyl substituted ammoniumcations eg. triethylammonium, tripropylammonium, tri(n-butyl)ammoniumand similar. Also suitable are N.N-dialkylanilinium cations such asN,N-dimethylanilinium cations.

The preferred ionic activators used as activators are those wherein thecation of the ionic activator comprises a hydrocarbyl substitutedammonium salt and the anion comprises an aryl substituted borate.

Typical borates suitable as ionic activators include:

-   triethylammonium tetraphenylborate-   triethylammonium tetraphenylborate,-   tripropylammonium tetraphenylborate,-   tri(n-butyl)ammonium tetraphenylborate,-   tri(t-butyl)ammonium tetraphenylborate,-   N,N-dimethylanilinium tetraphenylborate,-   N,N-diethylanilinium tetraphenylborate,-   trimethylammonium tetrakis(pentafluorophenyl) borate,-   triethylammonium tetrakis(pentafluorophenyl) borate,-   tripropylammonium tetrakis(pentafluorophenyl) borate,-   tri(n-butyl)ammonium tetrakis(pentafluorophenyl) borate,-   N,N-dimethylanilinium tetrakis(pentafluorophenyl) borate,-   N,N-diethylanilinium tetrakis(pentafluorphenyl) borate.

Particularly suitable activators of this type are those ionic activatorscomprising a cation and an anion wherein the anion has at least onesubstituent comprising a moiety having an active hydrogen,

Suitable activators of this type are described in WO 98/27119 therelevant portions of which are incorporated herein by reference.

Examples of this type of anion include:

-   triphenyl(hydroxyphenyl)borate-   tri (p-tolyl)(hydroxyphenyl)borate-   tris (pentafluorophenyl)(hydroxyphenyl)borate-   tris (pentafluorophenyl)(4-hydroxyphenyl)borate

Examples of suitable cations for this type of activator includetriethylammonium, triisopropylammonium, diethylmethylammonium,dibutylethylammonium and similar.

Particularly suitable are those cations having longer alkyl chains suchas dihexyldecylmethylammonium, dioctadecylmethylammonium,ditetradecylmethylammonium, bis(hydrogentated tallow alkyl)methylammonium and similar.

Particular preferred activators of this type are alkylammoniumtris(pentafluorophenyl) 4-(hydroxyphenyl) borates. A particularlypreferred activator is bis(hydrogenated tallow alkyl) methyl ammoniumtris (pentafluorophenyl) (4-hydroxyphenyl) borate.

The preferred method of preparation of the supported catalyst systems ofthe present invention comprises

-   -   (a) treatment of the suppport material with a source of a        transition metal atom    -   (b) addition of an activator, and    -   (c) addition of a transition metal compound.

The present invention is also suitable for use with traditional ZieglerNatta polymerisation catalyst systems wherein the support material istypically an inorganic metal halide for example magnesium chloride or aninorganic metal oxide for example silica.

Thus according to another aspect of the present invention there isprovided a supported catalyst system for the polymerisation of olefinscomprising

-   -   (a) a transition metal compound,    -   (b) a cocatalyst comprising an organometallic compound, and    -   (c) a support material comprising an inorganic metal oxide,        inorganic metal halide or polymeric material or mixtures thereof        characterised in that the support material has been pretreated        with a source of a transition metal atom.

Suitable transition metal compounds include those from Groups IVB-VIB(CAS Version), in particular compounds based on titanium compounds offormula MRx where M is titanium and R is halogen or a hydrocarbyloxygroup and x is the oxidation state of the metal. Such conventional typecatalysts include TiCl₄, TiBr₄, Ti(OEt)₃Cl, Ti(OEt)₂Br₂ and similar.

Traditional Ziegler Natta catalysts are described in more detail in“Ziegler-Natta Catalysts and Polymerisation” by J. Boor, Academic Press,New York, 1979.

Vanadium based catalysts include vanadyl halides eg. VCl₄, and alkoxyhalides and alkoxides such as VOCl₃, VOCl₂(OBu), VCl₃(OBu) and similar.

Other conventional transition metal compounds are those based onmagnesium/titanium electron donor complexes described for example inU.S. Pat. No. 4,302,565.

Particularly suitable transition metal compounds are those described inWO 9905187 and EP 595574.

Suitable organometallic compounds suitable as cocatalysts areorganoaluminium compounds for example trialkylaluminium compounds.

A preferred trialkylaluminium compound is triethylaluminum.

The supported catalyst systems of the present invention may comprisesystems wherein all the components are present on the support materialor alternatively may comprise systems wherein one or more of thecomponents may be introduced separately into the polymerisation reactor.

The supported catalyst systems of the present invention are mostsuitable for operation in processes which typically employ supportedpolymerisation catalysts.

The supported catalysts of the present invention may be suitable for thepolymerisation of olefin monomers selected from (a) ethylene, (b)propylene (c) mixtures of ethylene and propylene and (d) mixtures of(a), (b) or (c) with one or more other alpha-olefins.

Thus according to another aspect of the present invention there isprovided a process for the polymerisation of olefin monomers selectedfrom (a) ethylene, (b) propylene (c) mixtures of ethylene and propyleneand (d) mixtures of (a), (b) or (c) with one or more otheralpha-olefins, said process performed in the presence of a supportedcatalyst system as hereinbefore described.

The supported systems of the present invention are however most suitablefor use in slurry or gas phase processes.

A slurry process typically uses an inert hydrocarbon diluent andtemperatures from about 0° C. up to a temperature just below thetemperature at which the resulting polymer becomes substantially solublein the inert polymerisation medium. Suitable diluents include toluene oralkanes such as hexane, propane or isobutane. Preferred temperatures arefrom about 30° C. up to about 200° C. but preferably from about 60° C.to 100° C. Loop reactors are widely used in slurry polymerisationprocesses.

Gas phase processes for the polymerisation of olefins, especially forthe homopolymerisation and the copolymerisation of ethylene andα-olefins for example 1-butene, 1-hexene, 4-methyl-1-pentene are wellknown in the art.

Typical operating conditions for the gas phase are from 20° C. to 100°C. and most preferably from 40° C. to 85° C. with pressures fromsubatmospheric to 100 bar.

Particularly preferred gas phase processes are those operating in afluidised bed. Examples of such processes are described in EP 89691 andEP 699213 the latter being a particularly preferred process for use withthe supported catalysts of the present invention.

Particularly preferred polymerisation processes are those comprising thepolymerisation of ethylene or the copolymerisation of ethylene andα-olefins having from 3 to 10 carbon atoms.

Thus according to another aspect of the present invention there isprovided a process for the polymerisation of ethylene or thecopolymerisation of ethylene and α-olefins having from 3 to 10 carbonatoms, said process performed under polymerisation conditions in thepresent of a supported catalyst system as hereinbefore described.

The preferred α-olefins are 1-butene, 1-hexene, 4-methyl-1-pentene and1-octene.

The supported catalyst systems of the present invention may also besuitable for the preparation of other polymers for examplepolypropylene, polystyrene, etc.

When used for the polymerisation of olefins in a gas phase process thesupported catalyst systems of the present invention may reduce staticlevels on the resultant polymers thereby preventing the formation ofdeposits on the reactor walls and reducing fouling in the reactor. Thisis particularly the case for processes performed in a fluidised bedreactor and in particular for the copolymerisation of ethylene andalpha-olefins.

Thus according to another aspect of the present invention there isprovided a method for reducing the static charge on polymers prepared bya gas phase polymerisation of olefins in a fluidised bed reactor whereinsaid polymerisation is carried out in the presence of a supportedcatalyst system as hereinbefore described.

The present invention will now be further illustrated by reference tothe following examples:

Abbreviations

TEA triethylaluminium

TiBAl triisobutyaluminium

Ionic Activator A [N(H)Me(C₁₈H₃₇)₂][B(C₆F₅)₃(p-OHC₆H₄)]

Complex A (C₅Me₄SiMe₂N^(t)Bu)Ti(η⁴-1,3-pentadiene)

EXAMPLE 1

Preparation of Fe Sulfate Modified Silicas

To 20 g of silica Sylopol 948 was added the desired quantity (see tablebelow) of FeSO4 as water solutions (1% wt in Fe for silicas 1 and 2 and4.03% wt Fe for silica 3). Volume of FeSO4 [Fe] targeted [Fe] measuredSilica batch solution added (wt %) (wt %) 1 2 ml 0.1 0.1 2 10 ml  0.50.47 3 5 ml 1 0.88 4 0 0 0 (ref)Catalyst Preparations

EXAMPLE 2

To a suspension of 5.293 g of silica 2 (as described above) in hexane(30 ml) was added 10 ml of TEA (solution in hexane, [Al]=1.027 mol/l).The mixture was allowed to react for 30 minutes then the liquid fractionwas filtered and the remaining solid was washed with 3×20 ml of hexaneand finally dried under vacuum.

[Al]=1.48 mmol/g

To 1.485 ml of a toluene solution (11.1 wt %) of Ionic activator A wasadded 0.252 ml of a toluene solution of TEA ([Al]=0.25 mol/l). Thissolution was the added to 4 g of the above prepared silica/TEA and themixture was well agitated until non lumps were visible and was allowedto stand for 30 min. 0.705 ml of an heptane solution of Complex A (9.17%wt) was then impregnated. The mixture was well agitated untif non lumpswere visible and was allowed to stand for 30 min

10.42 ml of hexane were then added then the liquid fraction was filteredand the remaining solid was washed with 3×20 ml of hexane and finallydried under vacuum.

[Al]=1.41 mmol/g

[Ti]=31 μmol/g

[Fe]=0.084 mmol/g

EXAMPLE 3

To a suspension of 6.253 g of silica 1 (as described above) in hexane(30 ml) was added 10 ml of TEA (solution in hexane, [Al]=1.027 mol/l).The mixture was allowed to react for 30 minutes then the liquid fractionwas filtered and the remaining solid was washed with 3×20 ml of hexaneand finally dried under vacuum.

[Al]=1.46 mmol/g

To 1.485 ml of a toluene solution (11.1 wt %) of Ionic activator A wasadded 0.252 ml of a toluene solution of TEA ([Al]=0.25 mol/l). Thissolution was the added to 4 g of the above prepared silica/TEA and themixture was well agitated until non lumps were visible and was allowedto stand for 30 min. 0.705 ml of an heptane solution of Complex A (9.17%wt) was then impregnated. The mixture was well agitated until non lumpswere visible and was allowed to stand for 30 min

10.42 ml of hexane were then added then the liquid fraction was filteredand the remaining solid was washed with 3×20 ml of hexane and finallydried under vacuum.

[Al]=1.37 mmol/g

[Ti]=31 μmol/g

[Fe]=0.017 mmol/g

EXAMPLE 4

To a suspension of 5.737 g of silica 3 (as described above) in hexane(30 ml) was added 10 ml of TEA (solution in hexane, [Al]=1.027 mol/l).The mixture was allowed to react for 30 minutes then the liquid fractionwas filtered and the remaining solid was washed with 3×20 ml of hexaneand finally dried under vacuum.

[Al]=1.40 mmol/g

To 1.485 ml of a toluene solution (11.1 wt %) of Ionic activator A wasadded 0.252 ml of a toluene solution of TEA ([Al]=0.25 mol/l). Thissolution was the added to 4 g of the above prepared silica/TEA and themixture was well agitated until non lumps were visible and was allowedto stand for 30 min. 0.705 ml of an heptane solution of Complex A (9.17%wt) was then impregnated. The mixture was well agitated until non lumpswere visible and was allowed to stand for 30 min

10.42 ml of hexane were then added then the liquid fraction was filteredand the remaining solid was washed with 3×20 ml of hexane and finallydried under vacuum.

[Al]=1.35 mmol/g

[Ti]=31 μmol/g

[Fe]=0.15 mol/g

EXAMPLE 5 (COMPARATIVE)

To a suspension of 5.375 g of silica 4 (as described above) in hexane(30 ml) was added 10 ml of TEA (solution in hexane, [Al]=1.076 mol/l).The mixture was allowed to react for 30 minutes then the liquid fractionwas filtered and the remaining solid was washed with 3×20 ml of hexaneand finally dried under vacuum.

[Al]=1.44 mmol/g

To 1.485 ml of a toluene solution (11.1 wt %) of Ionic activator A wasadded 0.252 ml of a toluene solution of TEA ([Al]=0.25 mol/l). Thissolution was the added to 4 g of the above prepared silica/TEA and themixture was well agitated until non lumps were visible and was allowedto stand for 30 min. 0.705 ml of an heptane solution of Complex A (9.17%wt) was then impregnated. The mixture was well agitated until non lumpswere visible and was allowed to stand for 30 min

10.42 ml of hexane were then added then the liquid fraction was filteredand the remaining solid was washed with 3×20 ml of hexane and finallydried under vacuum.

[Al]=1.34 mmol/g

[Ti]=31 μmol/g

EXAMPLE 6

Preparation of Modified Silicas

To 20 g of silica Sylopol 948 was added the desired quantity of metalsalt as water solutions to target 1% metal in weight on the support. Thesilica was then calcined under nitrogen at 250° C. for 5 h. Silica batchMetal salt used (as aquous solution) A Iron sulfate B Copper sulfate CIron acetate D Comparative - no silica treatmentCatalyst Preparations

EXAMPLE 7

To a suspension of 5.737 g of silica A (as described above) in hexane(30 ml) was added 10 ml of TEA (solution in hexane, [Al]=1.027 mol/l).The mixture was allowed to react for 30 minutes then the liquid fractionwas filtered and the remaining solid was washed with 3×20 ml of hexaneand finally dried under vacuum.

[Al]=1.40 mmol/g

[Fe]=0.88 wt %

To 1.485 ml of a toluene solution (11.1 wt %) of Ionic Activator A wasadded 0.252 ml of a toluene solution of TEA ([Al]=0.25 mol/l). Thissolution was the added to 4 g of the above prepared silica/TEA and themixture was well agitated until non lumps were visible and was allowedto stand for 30 min. 0.705 ml of an heptane solution of Complex A (9.17%wt) was then impregnated. The mixture was well agitated until non lumpswere visible and was allowed to stand for 30 min

10.42 ml of hexane were then added then then the liquid fraction wasfiltered and the remaining solid was washed with 3×20 ml of hexane andfinally dried under vacuum.

[Al]=1.35 mmol/g

[Ti]=31 μmol/g

[Fe]=0.15 mmol/g

EXAMPLE 8

To a suspension of 5.732 g of silica B (as described above) in hexane(30 ml) was added 10 ml of TEA (solution in hexane, [Al]=1.047 mol/l).The mixture was allowed to react for 30 minutes then the liquid fractionwas filtered and the remaining solid was washed with 3×20 ml of hexaneand finally dried under vacuum.

[Al]=1.41 mmol/g

[Cu]=0.95 wt %

To 1.485 ml of a toluene solution (11.1 wt %) of Ionic Activator A wasadded 0.252 ml of a toluene solution of TEA ([Al]=0.25 mol/l). Thissolution was the added to 4 g of the above prepared silica/TEA and themixture was well agitated until non lumps were visible and was allowedto stand for 30 min. 0.705 ml of an heptane solution of Complex A (9.17%wt) was then impregnated. The mixture was well agitated until non lumpswere visible and was allowed to stand for 30 min

10.42 ml of hexane were then added then the liquid fraction was filteredand the remaining solid was washed with 3×20 ml of hexane and finallydried under vacuum.

μl]=1.41 mmol/g

[Ti]=33 μmol/g

[Cu]=0.13 mmol/g

EXAMPLE 9

To a suspension of 5.665 g of silica C (as described above) in bexane(30 ml) was added 10 ml of TEA (solution in hexane, [Al]=1.050 mol/l).The mixture was allowed to react for 30 minutes then the liquid fractionwas filtered and the remaining solid was washed with 3×20 ml of hexaneand finally dried under vacuum.

[Al]=1.35 mmol/g

[Fe]=0.83 wt %

To 1.485 ml of a toluene solution (11.1 wt %) of Ionic Activator A wasadded 0.252 ml of a toluene solution of TEA ([Al]=0.25 mol/l). Thissolution was the added to 4 g of the above prepared silica/TEA and themixture was well agitated until non lumps were visible and was allowedto stand for 30 min. 0.705 ml of an heptane solution of Complex A (9.17%wt) was then impregnated. The mixture was well agitated until non lumpswere visible and was allowed to stand for 30 min

10.42 ml of hexane were then added then the liquid fraction was filteredand the remaining solid was washed with 3×20 ml of hexane and finallydried under vacuum.

[Al]=1.35 mmol/g

[Ti]=29 μmol/g

[Fe]=0.145 mmol/g

EXAMPLE 10 (COMPARATIVE)

To a suspension of 10 g of silica D (as described above) in hexane (50ml) was added 7.4 ml of TEA (solution in hexane, [Al]=1.027 mol/l) and8.4 ml of TiBAl (solution in hexane, 0.952 mol/l). The mixture wasallowed to react for 30 minutes then the liquid fraction was filteredand the remaining solid was washed with 3×20 ml of hexane and finallydried under vacuum.

[Al]=1.35 mmol/g

To 1.485 ml of a toluene solution (11.1 wt %) of Ionic Activator A wasadded 0.252 ml of a toluene solution of TEA ([Al]=0.25 mol/l). Thissolution was the added to 4 g of the above prepared silica/(TEA+TiBAl)and the mixture was well agitated until non lumps were visible and wasallowed to stand for 30 min. 0.705 ml of an heptane solution of ComplexA (9.17% wt) was then impregnated. The mixture was well agitated untilnon lumps were visible and was allowed to stand for 30 min

10.42 ml of hexane were then added then the liquid fraction was filteredand the remaining solid was washed with 3×20 ml of hexane and finallydried under vacuum.

[Al]=1.28 mmol/g

[Ti]=31 [mol/g

Polymerisation Data

Gas Phase Polymerizations

The following gas phase examples for the copolymerisation of ethyleneand 1-hexene were carried using the above supported catalystcompositions. The gas phase procedure was as follows:

A 2.5 l double jacketed thermostatic stainless steel autoclave waspurged with nitrogen at 70° C. for at least one hour. 150 g of PEpellets previously dried under vacuum at 80° C. for 12 hours wereintroduced and the reactor was then purged three times with nitrogen (7bar to atmospheric pressure). ˜0.13 g of TEA treated silica (1.5 mmolTEA/g) was added under pressure and allowed to scavenge impurities forat least 15 minutes under agitation. The gas phase was then composed(addition of ethylene, 1-hexene and hydrogen) and a mixture of supportedcatalyst (˜0.1 g) and silica/TEA (˜0.1 g) was injected. A constantpressure of ethylene and a constant pressure ratio ofethylene/co-monomer were maintained during the run. The run wasterminated by venting the reactor and then purging the reactor 3 timeswith nitrogen. The PE powder produced during the run was then separatedfrom the PE seed bed by simple sieving. Typical conditions are asfollows:

Temperature: 70° C.

Ethylene pressure: 6.5 b Ethyl- 1- ene Hexene Hydrogen Catalyst Time RunCatalyst (bar) (ppm) (ml) (g) (hrs) 1 Example 2 6.5 5000 40 (+10 ml at0.101 1 yield 455 g/g) 2 Example 3 6.5 6100 40 (+10 ml at 0.1 1 yield400 g/g) 3 Example 4 6.5 5900 40 (+10 ml at 0.107 1 yield 520 g/g) 4Example 5 6.5 6300 40 0.100 1 (Com- parative) 5 Example 7 6.5 6200 50(+10 at 0.102 1.1 yield 500 g/g) 6 Example 8 6.5 6900 50 0.104 1 7Example 9 6.5 7600 50 (+10 at 0.101 1 yield 550 g/g) 8 Example 10 6.56500 50 0.098 1.1 (Com- parative)

NB. In all gas phase examples the agitation speed was 100 rev/min. Theactivities and the product characteristics are shown below-n Melt IndexActivity (2.16 kg) Density PE statics Run (g/g · hr/bar) g/10 min)(g/ml) (visual test) 1 95 0.801 0.9185 low 2 100 0.75 0.920 low 3 1011.254 0.9215 low 4 88 1.72 0.9205 high Electrostatic Activity Melt IndexDensity charge Run (g/mmol · h · bar) (2.16 kg) (g · ml) (KV/inch) 52720 1.8 0.926 −0.5 6 2130 0.74 0.917 −0.4 7 3003 0.74 0.922 −0.85 82520 1 0.927 −2

Electrostatic charges was measured under same conditions using a ValitecElectrostatic sensor on the polyethylene powder when downloaded from thereactor.

It is clear from the above examples that all the catalysts preparedbased on the treated silica supports show improved activities and lowerPE statics than the comparative examples.

EXAMPLE 11

30 g of ES70 silica was impregnated in a round bottomed flask with anaqueous solution of iron (ii) D-gluconate dihydrate (2.6 g in 15 mlwater). The resultant mixture was agitated for 30 minutes thenintroduced into a nitrogen fluidised silica calciner. Under a constantnitrogen flow the mixture was heated to 700° C., where upon thetemperature was maintained for 5 hours prior to cooling to ambienttemperature. A free flowing solid was recovered and used without furthermodification.

20 g of the silica was added to a glass reactor containing about 120 mlshexane and equipped with a stirrer. The slurry was stirred at 250 rpmand heated to 50° C. Dibutyl magnesium (DBM) was then added at an amountof 1 mmol per g. silica and the mixture stirred for 1 hour. Tetraethylorthosilicate (TEOS) at an amount 0.44 mmol per g. silica was then addedand the mixture stirred for 2 hours. Titanium tetrachloride (TiCl₄) wasthen added at an amount of 1 mmol per g. silica and the mixture stirredfor 1 hour. The catalyst was transferred to round bottomed flask and thevolatile components removed under reduced pressure.

EXAMPLE 12 Polymerisation

A stirred gas phase autoclave (2.5 L) was used for polymerisation usingthe catalyst prepared in example 11 in the presence of triethylaluminiumas cocatalyst. A seed bed was added to the reactor prior to compositionof the gas phase and heating to the reaction temperature. Followinginjection of the catalyst the ethylene pressure was maintained for 60minutes prior to emptying the reactor. 0.2008 g catalyst was used forthe polymerisation.

Polymerisation Conditions Ethylene   6 bar Hydrogen 2.5 barTriethylaluminium 0.7 mmol as 1M hexane solution Temperature 95° C.Yield 68.1 g polyethylene

1. A supported catalyst system suitable for the polymerisation ofolefins comprising (a) a transition metal compound, (b) an activatorcomprising (i) an aluminoxane or (ii) a Group IIIA (CAS Version) metalor metalloid compound, and (c) a support material comprising aninorganic metal oxide, inorganic metal halide or polymeric material ormixtures thereof wherein the support material has been pretreated with asource of a transition metal atom.
 2. A supported catalyst systemaccording to claim 1 wherein the support material is silica.
 3. Asupported catalyst system according to claim 1 wherein the transitionmetal compound is a metallocene.
 4. A supported catalyst systemaccording to claim 3 wherein the metallocene has the formula:CpMX_(n) wherein Cp is a single cyclopentadienyl or substitutedcyclopentadienyl group optionally covalently bonded to M through asubstituent, M is a Group VIB (CAS Version) metal bound in η⁵ bondingmode to the cyclopentadienyl or substituted cyclopentadienyl group, Xeach occurence is hydride or a moiety selected from the group consistingof halo, alkyl, aryl, aryloxy, alkoxy, alkoxyalkyl, amidoalkyl, andsiloxyalkyl [[etc.]] having up to 20 non-hydrogen atoms and neutralLewis base ligands having up to 20 non-hydrogen atoms or optionally oneX together with Cp forms a metallocycle with M and n is dependent uponthe valency of the metal.
 5. A supported catalyst system according toclaim 3 wherein the metallocene is represented by the general formula:

wherein: R′ each occurrence is independently selected from hydrogen,hydrocarbyl, silyl, germyl, halo, cyano, and combinations thereof, saidR′ having up to 20 nonhydrogen atoms, and optionally, two R′ groups(where R′ is not hydrogen, halo or cyano) together form a divalentderivative thereof connected to adjacent positions of thecyclopentadienyl ring to form a fused ring structure; X is a neutral η⁴bonded diene group having up to 30 non-hydrogen atoms, which forms aπ-complex with M; Y is —O—, —S—, —NR*—, —PR*—, M is titanium orzirconium in the +2 formal oxidation state; Z* is SiR*₂, CR*₂,SiR*₂SiR*₂, CR*₂CR*₂, CR*═CR*, CR*₂SiR*₂, or GeR*₂, wherein: R* eachoccurrence is independently hydrogen, or a member selected fromhydrocarbyl, silyl, halogenated alkyl, halogenated aryl, andcombinations thereof, said R* having up to 10 non-hydrogen atoms, andoptionally, two R* groups from Z* (when R* is not hydrogen), or an R*group from Z* and an R* group from Y form a ring system.
 6. A supportedcatalyst system according to claim 1 wherein the activator isrepresented by the formula:(L*−H)+_(d)(A^(d−)) wherein L* is a neutral Lewis base (L*−H)⁺ _(d) is aBronsted acid A^(d−) is a non-coordinating compatible anion of a GroupIIIA (CAS Version) metal or metalloid having a charge of d⁻, and d is aninteger from 1 to
 3. 7. A supported catalyst system according to claim 6wherein the activator comprises a cation and an anion wherein the anionhas at least one substituent comprising a moiety having an activehydrogen.
 8. A supported catalyst system according to claim 1 whereinthe activator is a fluorine containing Group IIIA metal or metalloidcompound.
 9. A supported catalyst system according to claims claim 1wherein the Group IIIA metal of the activator is boron.
 10. A supportedcatalyst system for the polymerisation of olefins comprising (a) atransition metal compound, (b) a cocatalyst comprising an organometalliccompound, and (c) a support material comprising an inorganic metaloxide, inorganic metal halide or polymeric material or mixtures thereofwherein the support material has been pretreated with a source of atransition metal atom.
 11. A supported catalyst system according toclaim 1 or 10 wherein the source of the transition metal atom is atransition metal salt.
 12. A supported catalyst system according toclaim 11 wherein the transition metal is iron or copper.
 13. A supportedcatalyst system according to claim 11 wherein the transition metal saltis ferrous sulphate, cupric sulphate or ferrous D-gluconate.
 14. Asupported catalyst system according to claim 1 or 10 wherein thetransition metal content on the support material is in the range 0.0001%to 10%.
 15. A process for the polymerisation of olefin monomers selectedfrom (a) ethylene, (b) propylene, (c) mixtures of ethylene and propyleneand (d) mixtures of (a), (b) or (c) with one or more otheralpha-olefins, said process performed under polymerisation conditions inthe presence of a supported catalyst system according to claim 1 or 10.16. A process for the polymerisation of ethylene or the copolymerisationof ethylene and alpha-olefins having from 3 to 10 carbon atoms, saidprocess performed under polymerisation conditions in the presence of asupported catalyst system according to claim 1 or
 10. 17. A processaccording to claim 15 wherein the alpha-olefins are selected from thegroup consisting of 1-butene, 1-hexene, 4-methyl-1-pentene and 1-octene.18. A process according to claim 15 carried out in the gas phase.